1. Field of the Invention
The present invention relates to an agitating pulverizer, and more particularly, to an agitating pulverizer which forms particulate matter with a desired particle size by agitating an object together with a binder within a tank by way of agitating vanes and by repeatedly granulating and pulverizing the object.
2. Description of the Related Art
In typical agitating pulverizers, a powder-like object charged into a tank is agitated while a suitable amount of binder is applied to the object and the object is further repeatedly granulated and pulverized, thereby forming the object into particulate matter with a suitable particle size.
Such agitating pulverizers are each provided with a pair of upper and lower agitating vanes which are rotatably provided within the tank. The object is agitated together with a binder while both being subjected to shearing force and centrifugal force and the object is repeatedly granulated and pulverized, thereby forming the object into particulate matter with a desired particle size. The pair of upper and lower agitating vanes are attached to the same rotating shaft and are rotated at the same speed in the same direction. Such a construction gives rise to a disparity of shearing force and centrifugal force between the central portion and the inner wall portion of the tank, which further sometimes causes the object to remain at the central portion of the tank and to adhere to the inner wall.
This makes it difficult to agitate the entire object uniformly, and thus, particulate matter with a uniform particle size cannot be formed.
In order to solve the foregoing problems, an agitating pulverizer constructed as follows has been suggested. A pair of upper and lower agitating vanes are rotatably provided within the tank, and the vanes are interconnected to the respective shafts which are rotated in different directions. Accordingly, the lower agitating vane is rotated at lower speed, while the upper vane is rotated at higher speed.
In the agitating pulverizer as described above, the object within the tank is drawn toward the center of the tank while being pushed upward by the lower vane which is rotated at lower speed, and consequently, a mountain-like object is formed near the leading portions in the rotating direction of the vanes.
The thus-obtained mountain-like object is subjected to shearing force while being pushed downward by the upper agitating vane which is rotated at higher speed. It is then agitated together with the binder charged into the tank and is repeatedly granulated and pulverized, thereby forming the object into particulate matter with a desired particle size.
However, the lower agitating vane is formed in such a way that the portion facing the bottom of the tank has a larger area, which increases resistance during the agitation of the object. Hence, the object is more likely to adhere to the bottom of the tank, thereby increasing power consumption.
Such an agitating pulverizer also presents the following problem. The agitating vanes only have a small force for pushing the object upward because of the configuration, which makes it difficult to agitate the entire object uniformly,-thereby failing to form particulate matter with a uniform particle size.
An agitating pulverizer which prevents an object from adhering to the bottom and the inner wall of a tank is disclosed in Japanese Patent Publication No. 59-21649.
In such an agitating pulverizer, an agitating vane is provided adjacent to the bottom of the tank, and a crushing vane is also provided within the tank farther upward of the agitating vane. The agitating vane and the crushing vane are interconnected to different rotating shafts so as to be rotatable in the same direction.
In the agitating pulverizer described above, the object charged into the tank is drawn toward the center of the tank by the projections provided at the outward ends of the agitating vane while being pushed upward by the rotation of the agitating vane at lower speed, thereby forming a mountain-like object at the leading portions in the rotating direction of the agitating vane.
The thus-obtained mountain-like object is pulverized while being subjected to shearing force by the rotation of the crushing vane at higher speed. The object is agitated together with the binder charged into the tank and is repeatedly granulated and pulverized, thereby forming the object into particulate matter with a desired particle size.
However, the agitating pulverizer as described above is constructed in such a way that the rotation center of a drive source for the agitating vane is placed substantially linearly with both outward ends of the agitating vane. This increases the load during the rotation, and thus, the object is likely to adhere to the bottom of the tank, and the force for pushing the object upward is decreased.
Hence, even though the crushing vane is rotated at higher speed, the entire object cannot be agitated uniformly, thereby failing to form particulate matter with a uniform particle size.
Additionally, if it is desired that a large tank for charging an object and a binder thereinto be employed, it requires a large amount of time and effort to assemble and dissemble the tank, and also it is extremely troublesome to perform maintenance, such as repairing and exchanging the agitating vane.